Creep forming a metallic component

ABSTRACT

A method of creep forming a metallic component is provided. The method includes the steps of applying static loading and cyclic loading and/or vibration to the component during the creep forming thereof to act as a source of additional energy.

This application is the US national phase of international applicationPCT/GB02/03061 filed 4 Jul. 2002, which designated the US.PCT/GB02/03061 claims priority to GB Application No. 0117066.1, filed 12Jul. 2001. The entire contents of these applications are incorporatedherein by reference.

This invention relates to the creep forming of metallic components.

Creep forming of metallic components by which a component such as analuminium alloy plate is laid on a former and heated while the plateslowly takes up the form of the former is well known.

This technique suffers from the disadvantage that forming can take along time, the tooling can be complex in shape to allow the correctprofile to be formed and factors such as springback must be taken intoaccount, requiring further processing steps and therefore can beuneconomic. Also the accuracy of formation can sometimes be inadequate,leading, for example, to the inability to produce large components ofcomplex shape such as aluminium alloy wingskin panels, where errors inthe shape formed accumulate over the length of the component tounacceptable levels above the required tolerances.

It is an object of the invention to provide an improved method of creepforming metallic components.

According to the invention there is provided a method of creep forming ametallic component including the steps of applying a static loading anda cyclic loading to the component during the creep forming thereof. Itis preferred that the magnitude of the cyclic loading is much smallerthan the magnitude of the static loading. The magnitude of the cyclicloading maybe less than or equal t 10% of the magnitude of the staticloading, more preferably it may be less than 5%. In the experimentsreported in this specification the magnitude of the cyclic loading isless than 2% of the magnitude of the static loading. Indeed it is lessthan 1%. A portion of the cyclic loading may be vibration.

The application of cyclic loading to components, artifacts, orstructures as an additional energy source during creep forming isbelieved to accelerate permanent deformation experienced by thecomponents and thus reduce springback. This is seen as a substantialadvancement on the prior art.

Allowing large components to be creep formed without an unacceptableaccumulation of error on the formed shape, tooling to be kept relativelysimple and forming times to be reduced, thus making the process moreeconomical. Excitation may be applied both globally and locally tocomponents, artifacts, or structures in either static or dynamic(adaptive) processing.

Methods of Application

Application of cyclic loading/vibration may be made either to alocalised component area, or to a whole component, depending upon sizeand specific forming requirements. Incremental application of thetechnique across a component will enable components of any dimension tobe treated. Components such as aircraft wing skins, stringers, spars,fuselage frames, fuselage panels etc. may be formed using thistechnique.

The technique is envisaged to be useful at any frequency over onecycle/hour.

Preferably frequencies of 20 Hz-10,000 Hz are used.

In principal this technique may be used regardless of component materialfor example with steels, titanium or aluminium and titanium andaluminium alloys. For some materials including the 2000, 6000, 7000, and8000 aluminium alloys cyclic loading can be applied as a supplement toconventional heating sources to increase strain retention during creepforming.

For materials where vibration/cyclic loading can be applied as asupplement to conventional heating sources to increase strain retentionduring creep forming this opens the exciting possibility of formingthese materials to the end required shape without further precipitationhardening and thus negating the need for further heat treatment. Thusallowing the forming process to take place during the last stage of heattreatment.

There are six major advantages of this technique:

-   1. An increase in strain retention during conventional or adaptive    processing at normal forming temperatures over conventional heating    when used alone.-   2. The ability to creep form materials, including 2000, 6000, 7000    and 8000 aluminium alloys in the final heat treatment stage for    example, 2024 aluminium alloy with a combination of conventional    heating to relatively low temperatures (up to 100° C.) with an    additional vibration/cyclic loading.-   3. Improved accuracy in final component shape as a direct result of    the control over the vibration wave form within the artifact or    component being processed.-   4. Improved process speed at normal forming temperatures.-   5. The ability to exercise forming zone control as a result of the    local application of vibration/cyclic loading in thickened areas    such as local reinforcements or integrally stiffened areas of    components.-   6. The ability to time curvature on large components such as large    aircraft wing skins and stringers.    Equipment

Portable excitation equipment is preferably used in the case of localapplication of the technique to a discrete area of a component.Otherwise bespoke equipment may be used for large components, forexample aircraft wing skin panels.

The invention will now be further explained by way of example only withreference to the accompanying drawings of which:

FIG. 1 is a graphical representation of the Stress Relaxation withAgeing Time results from displacement control tests carried out on 2024T351 aluminium alloy for ten hours at 155° C. plus or minus 5° C.

FIG. 2 is a graphical representation of the Stress Relaxation withAgeing Time results from displacement control tests carried out on 7150W51 aluminium alloy for ten hours at 155° C. plus or minus 5° C.

FIG. 3 is a graphical representation of the Creep Displacement withAgeing Time results from displacement control tests carried out on 7150W51 aluminium alloy for ten hours at 155° C. plus or minus 5° C.

FIG. 4 is a graphical representation of the total Creep AgeingDisplacement left after the tests represented in FIGS. 1-3.

Experimental Data

There follows a description of the testing of bent-beam cyclic creepforming specimens for two aluminium alloys; 2024 T351 and 7150 W51 andthe subsequent results.

Experimental Method

The tests involved the quantitative stressing of beam specimens byapplication of a four point bending stress using a servohydraulic cyclicinstron machine. The applied stress was determined from the size of thespecimen and the bending deflection. The stressed specimens were thenexposed to a test temperature and a cyclic load of small amplitudeapplied. Displacements along the length of the beam specimens were thenmeasured and reported.

The stresses and displacements were calculated using the followingformula:σ_(max)=12×E×t×y/(3×H ²−4×A ²)  (1)Where:

-   -   σ: maximum tensile stress    -   E: modulus of elasticity=73 GPa    -   t: thickness of specimen=0.0035 m    -   y: maximum displacement    -   H: distance between outer supports=0.180 m    -   A: distance between inner and outer supports=0.045 m        Displacement Controlled Tests

The displacements shown in below in Tables 1 and 3 were kept constantduring the tests. The loads were measured at given intervals. Thepermanent displacement left after the tests was measured along thelength of the specimens.

2024 T351 Aluminium Alloy

The displacements applied to the specimens of 2024 T351 aluminium alloyfor the stresses selected, as calculated by equation (1), were asfollows:

TABLE 1 Applied Displacements Max. Displacement Cyclic DisplacementStress (MPa) (m) +/− (m) 230 0.006684 232.5 (230 +/− 2.5) 0.0067560.000072 235 (230 +/− 5) 0.006830 0.000146The loadings applied were:

$\begin{matrix}{\sigma_{\max} = \frac{3 \times A \times W}{b \times d^{2}}} & (2)\end{matrix}$Where: W: Load (MN)

-   -   A: Distance between inner and outer supports    -   b: Specimen width (0.05 m)    -   d: Specimen thickness (0.0035 m)

TABLE 2 Applied loads Stress W load Cyclic load (MPa) (KN) +/− (KN) 2301.044 232.5 1.055 0.011 235 1.066 0.0227150 W51 Aluminium Alloy

The Displacements applied to the specimens of 7150 W51 aluminium alloyand for the stresses selected, as calculated by equation (1), were asfollows:

TABLE 3 Applied Displacements Max. Displacements Cyclic DisplacementStress (MPa) (m) +/− (m) 350 0.01017 352.5 (350 +/− 2.5) 0.0102440.000074 355 (350 +/− 5) 0.0103165 0.0001465

The loadings applied as calculated by equation (2) were:

TABLE 4 Applied loads W load Cyclic load Stress (MPa) (KN) +/− (KN) 3501.588 352.5 (350 +/− 2.5) 1.6 0.012 255 (350 +/− 5) 1.611 0.023

Forming time is defined as the time from the inception of the test untilthe required time has elapsed. The above tests began when the stressedspecimen achieved the required temperature.

The Forming time was 10 hours (±15 minutes). The temperature was 155°C.±5° C.

Load Controlled Tests (7150 W51 Aluminium Alloy)

The load was maintained at 350 MPa in the static test and 350+/−2.5 MPaor +/−5 MPa in the tests with a small cyclic load. The specimens werethen left to creep. The Forming time was 10 hours (±15 minutes). Thetemperature was 155° C.±5° C.

Results

Displacement Controlled Tests

2024 T351 ALLOY Test 1—Static Load Only 10 hrs at 155° C.

TABLE 5 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.105 0.142 0.16 0.102 After Test 0 0.2950.412 0.34 0.05

TABLE 6 Load Relaxation Time Load Stress (hrs) (KN) (MPa) 0 1.04 230 10.75 165 2 0.67 148 3 0.64 141 4 0.62 137 5 0.62 137 6 0.62 137

Test 2—Static Load plus +/−2.5 MPa cyclic load—25 Hz 10 hrs at 155° C.

TABLE 7 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.06 0.072 0.09 0.04 After Test 0 0.2850.405 0.34 0.05

TABLE 8 Load Relaxation Time Load Stress (hrs) (KN) (MPa) 0 1.04 230 10.78 172 2 0.67 148 3 0.64 141 4 0.64 141 5 0.64 141 6 0.64 141

Test 3—Static Load plus +/−2.5 MPa cyclic load—50 Hz 10 hrs at 155° C.

TABLE 9 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.135 0.155 0.107 −0.05 After Test 0 0.360.463 0.32 −0.055

TABLE 10 Load Relaxation Time Load Stress (hrs) (KN) (MPa) 0 1.043 230 10.78 172 2 0.69 152 3 0.66 146 4 0.65 143 5 0.65 143 6 0.65 143

Test 4—Static Load plus +/−5 MPa cyclic load—25 Hz 10 hrs at 155° C.

TABLE 11 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.0125 0.0175 −0.03 −0.04 After Test 00.19 0.276 0.162 −0.06

TABLE 12 Load Relaxation Time Load Stress (hrs) (KN) (MPa) 0 1.043 230 10.79 174 2 0.69 152 3 0.64 141 4 0.63 139 5 0.63 139 6 0.63 139

Test 5—Static Load plus +/−5 MPa cyclic load—50 Hz 10 hrs at 155° C.

TABLE 13 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.0225 0.02 0.00 −0.05 After Test 0 0.3050.401 0.3 −0.05

TABLE 14 Load Relaxation Time Load Stress (hrs) (KN) (MPa) 0 1.042 230 10.83 183 2 0.71 156 3 0.67 148 4 0.65 143 5 0.65 143 6 0.65 143

Repeated Test Test 4A—Static Load plus +/−5 MPa cyclic load—25 Hz 10 hrsat 155° C.

TABLE 15 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.03 0.025 0.04 0.02 After Test 0 0.2100.285 0.220 0.05

TABLE 16 Load Relaxation Time Load Stress (hrs) (KN) (MPa) 0 1.046 230 10.81 179 2 0.69 152 3 0.66 145 4 0.64 141 5 0.64 141 6 0.63 139

The Stress Relaxation with Ageing Time results from displacement controltests carried out on 2024 T351 aluminium alloy for ten hours at 155° C.plus or minus 5° C. are shown in a graphical representation in FIG. 1.

7150 W51 ALLOY Test 1—Static Load Only 10 hrs at 155° C.

TABLE 17 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 −0.015 0 0.03 0.05 After Test 0 1.4652.17 1.645 0.16

TABLE 18 Load Relaxation Time (hrs) Load (KN) Stress (MPa) 0 1.585 350 11.453 320 2 1.361 300 3 1.333 294 4 1.302 287 5 1.288 284 6 1.287 284

Test 2—Static Load plus +/−2.5 MPa cyclic load—25 Hz 10 hrs at 155° C.

TABLE 19 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.005 0 −0.02 −0.04 After Test 0 1.432.09 1.55 0.025

TABLE 20 Load Relaxation Time (hrs) Load (KN) Stress (MPa) 0 1.585 350 11.270 280 2 1.155 255 3 1.097 242 4 1.079 238 5 1.071 236 6 1.060 234 71.053 232 8 1.047 231

Test 3—Static Load plus +/−5 MPa cyclic load—25 Hz 10 hrs at 155° C.

TABLE 21 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.13 0.1 0.05 −0.075 After Test 0 1.402.03 1.485 0.01

TABLE 22 Load Relaxation Time (hrs) Load (KN) Stress (MPa) 0 1.589 350 11.166 257 2 0.972 214 3 0.912 201 4 0.872 192 5 0.851 188 6 0.837 184 70.828 182 8 0.825 182

Test 4—Static Load plus +/−2.5 MPa cyclic load—50 Hz 10 hrs at 155° C.

TABLE 23 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.145 0.155 0.04 −0.085 After Test 01.640 2.32 1.58 −0.05

TABLE 24 Load Relaxation Time (hrs) Load (KN) Stress (MPa) 0 1.554 350 11.302 287 2 1.141 251 3 1.110 245 4 1.088 240 5 1.070 236 6 1.058 233 71.050 231 8 1.045 230

Test 5—Static Load plus +/−5 MPa cyclic load—50 Hz 10 hrs at 155° C.

TABLE 25 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.2 0.28 0.2 0 After Test 0 1.22 1.811.35 0.08

TABLE 26 Load Relaxation Time (hrs) Load (KN) Stress (MPa) 0 1.587 350 11.116 246 2 1.027 226 3 0.987 218 4 0.968 213 5 0.962 212 6 0.958 211 70.948 209 8 0.942 208

The Stress Relaxation with Ageing Time results from displacement controltests carried out on 7150 W51 aluminium alloy for ten hours at 155° C.plus or minus 5° C. are shown in a graphical representation in FIG. 2.

7150 W51 Aluminium Alloy Load Controlled Tests

7150 W51 ALLOY Load Control (Load 1.588 KN) Test 1—Static Load Only 10hrs at 155° C.

TABLE 27 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.42 0.66 0.57 0.06 After Test 0 2.954.14 3.19 0.26

TABLE 28 Displacement vs Time Actuator position Displacement Time (hrs)(mm) (mm) 0   1.127 0 1 −0.504 1.631 1.5 −0.936 2.063 2 −1.225 2.352 3 −1.4012 2.528 4 −1.631 2.758 5 −1.852 2.979 6 −2.043 3.17 7 −2.1813.308 Note This specimen was initially loaded for 15 min at 155° C. to astress of 230 MPa. The specimen was then unloaded, cooled to roomtemperature and the test re-started as above. Hence the initialcurvature of 0.66 mm at the centre.

Load Control (Load 1.588 KN) Test 2—Static Load plus +/−2.5 MPa cyclicload—25 Hz 10 hrs at 155° C.

TABLE 29 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.33 0.43 0.25 −0.03 After Test 0 2.223.14 2.145 −0.04

TABLE 30 Displacement vs Time Actuator position Displacement Time (hrs)(mm) (mm) 0   1.454  0 1   0.416  1.038 2 −0.0673 1.521 3 −0.2665 1.72 4−0.3625 1.816 5 −0.4431 1.897 6 −0.4413 1.895 7 −0.5544 2.001

Load Control (Load 1.588 KN) Test 3—Static Load plus +/−5 MPa cyclicload—25 Hz 10 hrs at 155° C.

TABLE 31 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.145 0.2 0.125 0.03 After Test 0 1.652.305 1.685 0.09

TABLE 32 Displacement vs Time Actuator position Displacement Time (hrs)(mm) (mm) 0 3.331 0 1 2.184 1.147 2 2.122 1.209 3 1.953 1.378 4 1.8831.448 5 1.809 1.552 6 1.734 1.597 7 1.690 1.641 8 1.673 1.658 9 1.6451.686

Load Control (Load 1.588 KN) Test 4 (Repeat of Test 2)—Static Load plus+/−2.5 MPa cyclic load—25 Hz 10 hrs at 155° C.

TABLE 33 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.022 0.0725 0.095 0.095 After Test 01.59 2.29 1.62 0.115

TABLE 34 Displacement vs Time Actuator position Displacement Time (hrs)(mm) (mm) 0   2.357  0 1   0.6209 1.736 2   0.086  2.271 3 −0.3268 2.6844 −0.2934 2.65 5 −0.3097 2.667 6 −0.4321 2.789 7 −0.5198 2.877

Load Control (Load 1.588 KN) Test 5 (Repeat of Test 3)—Static Load plus+/−5 MPa cyclic load—25 Hz 10 hrs at 155° C.

TABLE 35 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.055 0.085 0.095 0.075 After Test 0 1.001.435 1.075 0.05

TABLE 36 Displacement vs Time Actuator position Displacement Time (hrs)(mm) (mm) 0 2.475 0 1 0.8531 1.622 2 0.6984 1.777 3 0.3650 2.11 4−0.3936 2.869 Note: The machine shut down after 4 hrs testing

Load Control (Load 1.588 KN) Test 6—Static Load plus +/−2.5 MPa cyclicload—40 Hz 10 hrs at 155° C.

TABLE 37 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.13 0.17 0.13 −0.01 After Test 0 1.5652.17 1.55 0.03

TABLE 38 Displacement vs Time Actuator position Displacement Time (hrs)(mm) (mm) 0 2.061 0 1 0.7958 1.265 2 0.3590 1.702 3 0.1265 1.935 40.7396 1.321 5 0.6557 1.405 6 0.6336 1.427 7 0.6373 1.424 Note: Thefrequency was 40 Hz (instead of 50 Hz) due to instability on the signalat 50 Hz.

Load Control (Load 1.588 KN) Test 7—Static Load plus +/−5 MPa cyclicload—40 Hz 10 hrs at 155° C.

TABLE 39 Specimen Displacements (mm) Distance from edge (mm) 125 45 90(centre) 170 215 Before Test 0 0.07 0.08 0.025 −0.105 After Test 0 2.73.88 2.83 0.04

TABLE 40 Displacement vs Time Actuator position Displacement Time (hrs)(mm) (mm) 0 1.962 0 1 −3.094 5.056 2 −3.247 5.209 3 −3.580 5.542 4−3.629 5.591 5 −3.764 5.726 6 −3.892 5.854 7 −3.900 5.862 Note: Thefrequency was 40 Hz (instead of 50 Hz) due to instability on the signalat 50 Hz.

Creep Displacement with Ageing Time results from displacement controltests carried out on 7150 W51 aluminium alloy for ten hours at 1550Cplus or minus 50C are shown in a graphical representation in FIG. 3.

The data showing the permanent displacement left at the end of all ofthe tests is shown graphically in FIG. 4.

Observations

From the results of the displacement controlled tests outlined above andit was observed that there was very little influence of the smallamplitude cyclic loading is observed on the age-forming of 2024 T351Aluminium Alloy. This can be seen clearly from the graphicalrepresentation at FIG. 1. The specimen subjected to static loading alonecreep-aged at approximately the same rate as those that also included asmall amplitude cyclic loading.

Conversely, the 7150 W51 Aluminium Alloy displacement controlled testsresults showed a definite effect of the small cyclic loading on thecreep-aged rate as illustrated in FIG. 2. For example, the stressrelaxed to a low value of 180 MPa from an initial stress of 350 MPa whenthe loading included small amplitude cycling (+/−5 MPa (25 Hz)) while,with static loading alone, it relaxed from an initial stress of 350 MPato only 284 MPa in the same time span.

From these results it also seems possible that the magnitude of thestress relaxation is dominated by the range of the small amplitudecycles, i.e. the +/−5 MPa tests showed a larger stress relaxation thanthe +/−2.5 MPa.

In the Load Controlled Tests indicate results showed that the specimentested at +/−5 MPa and 40 Hz frequency showed a substantially highercreep elongation than the other specimens tested. Thus a combination ofcyclic amplitude and high frequency seems to produce higher creepelongation.

The graphical representation of the permanent deflection left at the endof all of the tests as shown in FIG. 4, clearly shows that the 7150 W51Aluminium Alloy retained a much higher permanent deflection than the2024 T351 Aluminium Alloy after the Displacement Controlled tests.

The data from the load controlled tests showed a much higher scatterthan that from the displacement controlled tests. It should be notedthat the very low amplitude cyclic loading was very difficult to controlbecause they were of the same magnitude as the noise, this can explainthe larger scatter in the results of in this type of test.

Discussion

7150 Aluminium Alloy seems to age-creeps more readily than 2024Aluminium Alloy. This may be the result of two factors. Firstly, thestresses applied to the 7150 W51 Aluminium Alloy were higher than thoseapplied to the 2024 T351 Aluminium Alloy (350 MPa against 230 MPa).Obviously, 7150 Aluminium Alloy being a stronger material than the 2024Aluminum Alloy can be subjected to higher stresses. For example, theratio of the yield stresses when fully aged are 1.63 while the ratios ofthe applied stresses in the tests was 1.52. Secondly, the is 2024Aluminium Alloy was already aged to a temper T351 while the 7150Aluminium Alloy was not artificially aged prior to testing. This meansthat the 7150 Aluminium alloy material tested was initially softer thanthe 2024 Aluminium Alloy fully aged material tested, which may result ina higher creep rate than may be anticipated by the ratio of 1.52mentioned above.

From these results the potential for a method of creep forming metalliccomponents including a step of applying cyclic loading/vibration is verygood. Such a technique will enable large components to be creep formedeconomically, whilst maintaining the necessary accuracy and thus keepingthe component within the required tolerance.

1. A method of creep forming a metallic component including the steps ofapplying a static loading and a cyclic loading to the component duringthe creep forming thereof, wherein the magnitude of the cyclic loadingis less than or equal to 10% of the magnitude of the static loading,wherein the cyclic loading has a frequency of 1 Hz to 1,000 Hz.
 2. Amethod of creep forming a metallic component as in claim 1 wherein themagnitude of the cyclic loading is less than or equal to 5% of themagnitude of the static loading.
 3. A method of creep forming a metalliccomponent as in claim 2 wherein the magnitude of the cyclic loading isless than or equal to 2% of the magnitude of the static loading.
 4. Amethod of creep forming a metallic component as in claim 3 wherein themagnitude of the cyclic loading is less than or equal to 1% of themagnitude of the static loading.
 5. A method of creep forming a metalliccomponent as in claim 1 wherein a portion of the cyclic loading isvibration.
 6. A method of creep forming a metallic component as in claim1 wherein the cyclic loading has a frequency of 10 Hz to 100 Hz.
 7. Amethod of creep forming a metallic component as in claim 6 wherein thecyclic loading has a frequency of 20 Hz to 50 Hz.
 8. A method of creepforming a metallic component as in claim 1 wherein the metalliccomponent is formed from a metal alloy.
 9. A method of creep forming ametallic component as in claim 8 wherein the metal alloy is an aluminiumalloy.
 10. A method of creep forming a metallic component as in claim 1wherein the metallic component is creep formed during a final stage ofheat treatment of a material from which the metallic component isformed.
 11. A method of creep forming a metallic component including thesteps of applying a static loading and a cyclic loading to the componentduring the creep forming thereof, wherein the magnitude of the cyclicloading is less than or equal to 10% of the magnitude of the staticloading, wherein the cyclic loading is applied to a discrete portion ofthe component and the cyclic loading is applied to successive portionsof the component until substantially the whole component has been creepformed.
 12. A method of creep forming a metallic component as in claim11 in which a said discrete portion of the component is a zone ofstructural reinforcement of the component.
 13. A method of creep forminga metallic component including the steps of: applying a static loadingon the order of 350 MPa; and simultaneously with the application of saidstatic loading, applying a cyclic loading at a frequency on the order of40 Hz and a loading on the order of ±5 MPa to the component during thecreep forming thereof.
 14. A method of creep forming a metalliccomponent according to claim 13, wherein said metallic component is analuminum alloy.
 15. A method of creep forming a metallic componentaccording to claim 14, wherein said aluminum alloy is 7150 W51 aluminumalloy.